Brain activity is contingent on neuropsychological function in a functional magnetic resonance imaging study of verbal working memory in amyotrophic lateral sclerosis

Abstract

Background and purpose: Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that causes progressive degeneration of neurons in motor and non-motor brain regions, affecting multiple cognitive domains such as memory. A functional magnetic resonance imaging (fMRI) study was performed to explore working memory function in ALS.

Methods: To contribute to the growing research field that employs structural and functional neuroimaging to investigate the effect of ALS on different working memory components, the localization and intensity of alterations in neural activity was explored using fMRI. Being the first study to specifically address verbal working memory via fMRI in the context of ALS, the verbal n-back task with 0-back and 2-back conditions was employed.

Results: Despite ALS patients showing unimpaired accuracies (p = 0.724) and reaction times (p = 0.0785), there was significantly increased brain activity of frontotemporal and parietal regions in the 2-back minus 0-back contrast in patients compared to controls (using nonparametric statistics with 5000 permutations and a T threshold of 2.5).

Discussion: Increased brain activity of the frontotemporal and parietal regions during working memory performance was largely associated with better neuropsychological function within the ALS group, suggesting a compensatory effect during working memory execution. This study therefore adds to the current knowledge on neural correlates of working memory in ALS and contributes to a more nuanced understanding of hyperactivity during cognitive processes in fMRI studies of ALS.

Keywords: amyotrophic lateral sclerosis; fMRI; neuroimaging; neuropsychology; working memory.